Fructose and Sucrose Intake Increase Exogenous  Carbohydrate Oxidation during Exercise

Abstract

Peak exogenous carbohydrate oxidation rates typically reach ~1 g∙min−1 during exercise when ample glucose or glucose polymers are ingested. Fructose co‐ingestion has been shown to further increase exogenous carbohydrate oxidation rates. The purpose of this study was to assess the impact of fructose co‐ingestion provided either as a monosaccharide or as part of the disaccharide sucrose on exogenous carbohydrate oxidation rates during prolonged exercise in trained cyclists. Ten trained male cyclists (VO2peak: 65 ± 2 mL∙kg−1∙min−1) cycled on four different occasions for 180 min at 50% Wmax during which they consumed a carbohydrate solution providing 1.8 g∙min−1 of glucose (GLU), 1.2 g∙min−1 glucose + 0.6 g∙min−1 fructose (GLU + FRU), 0.6 g∙min−1 glucose + 1.2 g∙min−1 sucrose (GLU + SUC), or water (WAT). Peak exogenous carbohydrate oxidation rates did not differ between GLU + FRU and GLU + SUC (1.40 ± 0.06 vs. 1.29 ± 0.07 g∙min−1, respectively, p = 0.999), but were 46% ± 8% higher when compared to GLU (0.96 ± 0.06 g∙min−1: p < 0.05). In line, exogenous carbohydrate oxidation rates during the latter 120 min of exercise were 46% ± 8% higher in GLU + FRU or GLU + SUC compared with GLU (1.19 ± 0.12, 1.13 ± 0.21, and 0.82 ± 0.16 g∙min−1, respectively, p < 0.05). We conclude that fructose co‐ingestion (0.6 g∙min−1) with glucose (1.2 g∙min−1) provided either as a monosaccharide or as sucrose strongly increases exogenous carbohydrate oxidation rates during prolonged exercise in trained cyclists.

Keywords

• substrate utilization
•  stable isotopes
•  metabolism
•  sugar